AD8226ARZ Analog Devices Inc, AD8226ARZ Datasheet - Page 24

• Manufacturer Part Number: AD8226ARZ
• Description: Precision InAmp
• Manufacturer: Analog Devices Inc

Specifications of AD8226ARZ

• Amplifier Type: Instrumentation
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• Slew Rate: 0.6 V/µs
• -3db Bandwidth: 1.5MHz
• Current - Input Bias: 20nA
• Voltage - Input Offset: 200µV
• Current - Supply: 350µA
• Current - Output / Channel: 13mA
• Voltage - Supply, Single/dual (±): 2.2 V ~ 36 V, ±1.35 V ~ 18 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• No. Of Amplifiers: 1
• Input Offset Voltage: 200µV
• Bandwidth: 1.5MHz
• Amplifier Output: Rail To Rail
• Cmrr: 80dB
• Supply Voltage Range: ± 1.35V To ± 18V
• Supply Current: 350µA
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Gain Bandwidth Product: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD8226
PRECISION STRAIN GAGE
The low offset and high CMRR over frequency of the AD8226
make it an excellent candidate for performing bridge measure-
ments. The bridge can be connected directly to the inputs of the
amplifier (see Figure 65).
DRIVING AN ADC
Figure 66 shows several methods for driving an ADC. The
ADuC7026
contains ADCs with an unbuffered, charge-sampling architecture
that is typical of most modern ADCs. This type of architecture
typically requires an RC buffer stage between the ADC and
amplifier to work correctly.
350Ω
350Ω
microcontroller was chosen for this example because it
350Ω
350Ω
Figure 65. Precision Strain Gage
10µF
0.1µF
AD8226
AD8226
AD8226
R
+15V
–15V
G
3.3V
3.3V
+IN
–IN
5V
+
–
OPTION 1: DRIVING LOW FREQUENCY SIGNALS
OPTION 2: DRIVING HIGH FREQUENCY SIGNALS
OPTION 3: PROTECTING ADC FROM LARGE VOLTAGES
AD8226
REF
REF
REF
100Ω
10kΩ
2.5V
AD8616
AD8616
100nF
3.3V
3.3V
Figure 66. Driving an ADC
Rev. B | Page 24 of 28
10Ω
10Ω
Option 1 shows the minimum configuration required to drive
a charge-sampling ADC. The capacitor provides charge to the
ADC sampling capacitor while the resistor shields the AD8226
from the capacitance. To keep the AD8226 stable, the RC time
constant of the resistor and capacitor needs to stay above 5 µs.
This circuit is mainly useful for lower frequency signals.
Option 2 shows a circuit for driving higher speed signals. It uses a
precision op amp (AD8616) with relatively high bandwidth and
output drive. This amplifier can drive a resistor and capacitor with
a much higher time constant and is therefore suited for higher
frequency applications.
Option 3 is useful for applications where the AD8226 needs to
run off a large voltage supply but drive a single-supply ADC.
In normal operation, the AD8226 output stays within the ADC
range, and the AD8616 simply buffers it. However, in a fault
condition, the output of the AD8226 may go outside the supply
range of both the AD8616 and the ADC. This is not an issue in
the circuit, however, because the 10 kΩ resistor between the two
amplifiers limits the current into the AD8616 to a safe level.
10nF
10nF
ADC0
ADC1
ADC2
ADuC7026
AGND
AV
3.3V
DD